Prove that: `t a n 70^0=t a n 20^0+2t a n 50^0dot`

1.	Prove that: `t a n 70^0=t a n 20^0+2t a n 50^0dot`
Answer» `70^(@)=20^(@)+50^(@)` `rArr tan70^(@)=tan(20^(@)+50^(@))` `rArr tan70^(@)-tan70^(@)tan20^(@)tan50^(@)=tan20^(@)+tan50^(@)=tan20^(@)+tan50^(@)` `tan70^(@)-cot20^(@).1/(cot20^(@))tan50^(@)=tan20^(@)+tan50^(@)` `rArr tan70^(@)-tan50^(@)=tan20^(2)+tan50^(@)` `rArr tan70^(@)=tan20^(@)+2tan50^(2)` Hence proved.

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